The variability of organic matter across four contrasting land uses namely oil palm plantation OPPL, sand mining site SM,  tenuously cultivated land CCL and primary Forest (PFL) were evaluated in Imo State. Results obtained showed that the percentage of sand decreased down the depths in all the land uses: PFL, CCL, OPPL, SM which were 76.6, 76.1, 77.7 and 70% respectively. The soils ranged from sandy loam to sandy clay loam in texture. The SM had the highest mean bulk density of 1.76 g/cm3 against the lowest mean value of 1.52 g/cm3 in the PFL. Similarly the PFL had the highest mean percentage organic matter of 2.12% as well as the lowest coefficient of variation 7.8% compared to the high coefficient of variations observed in the other land uses. The sand mining had 68% coefficient of variation while the CCL, OPPL had coefficient variations of 58% and 52% respectively indicating high variations .There was little or no variations in the percentage total nitrogen as well as available phosphorus in the PFL compared to the high variation in the other land uses. Land uses that depleted the essential nutrients in the soil should be avoided. Mulching and conservation tillage that tends to restore the soils nutrient ability should be adopted and sustained.

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The present study investigated the combined effect of rice husk dust (RHD) (0.1.2.3.4 and 5 ton ha-1) and NPK 10:10:10 fertilizer (0, 1, 2, 3, 4 and 5 ton ha-1) arranged factorially in Randomized Complete Block Design(RCBD)on selected soil fertility indices (pH, organic carbon, organic matter, total nitrogen, available phosphorus, exchangeable bases, exchangeable acidity and effective cation exchange capacity) and growth parameters of Jatropha (number of leaves, plant height, number of branches and stem girth) in an ultisol of southeastern Nigeria. Results showed significant (P<0.05) improvement in all soil chemical properties and growth parameters of plant compared to control which had no treatment. However, the effects varied with treatment levels and interactions. While the effects increased with rate of application, interactions consistently showed superior effect on all parameters studied. Thus, combining rice husk dust (RHD) and NPK may increase the soil fertility and growth of Jatropha. Treatments combination of5tonha-1 RHD and 3tonha-1 NPK and 5tonha-1 RHD and 5tonha-1 NPK relatively gave the most appreciable result in soil chemical properties and growth of Jatropha respectively, thus are recommended.

In this study, we investigated the fruit, seed yield and biofuel production potentials of Jatropha curcas in soils fertilized with different rates of rice husk dust (RHD) and NPK 10:10:10. This study took place at the Teaching and Research Farm of the Department of Horticulture and Landscape Technology, Akanu Ibiam Federal Polytechnic, Unwana from April 2020 to March 2021. Treatments comprised of six rates (0, 1,2,3,4 and 5 ton ha-1) each of RHD and NPK, arranged in Randomized Complete Block Design (RCBD in Randomized Complete Block Design (RCBD) in a factorial pattern. Nursery Jatropha seedling of average heights of about 30 cm and 5-6 true leaves were transplanted to the field a month after treatment application. Our measurement between 10 to 12 months of Jatropha growth focused on the number of fruits, weight of fruits, number of seeds, weight of seeds and quantity of oil per plant. Analysis of variance (ANOVA) and Least Significant Difference (LSD) tools were used to analyze the obtained data and separated the significant means respectively. The relationship between yield parameters and selected soil chemical properties was determined using correlation analysis. Results indicated that relative to control, addition of RHD and NPK as lone and combined treatments increased the fruit, seed yield and oil quantity of Jatropha. Relative to control, fruit number increased by 72.80%, fruit weight by 79.81% and number of seeds by 80.73%. Similarly, the seed weight and oil content increased by 28.11% and 21.485 respectively. Organic matter, available phosphorus and total nitrogen had highly significant correlation with fruit, seed yield and oil quantity. Treatments combination of 5tonha-1 RHD and 5tonha-1 relatively gave the most appreciable result in fruit, seed yield and oil quantity and therefore recommended.